MOBILE APPS

Consumers use their mobile devices and websites are accessed via mobile more and more every day. All research seems to agree on this point.
Developing mobile apps is not simple. The device base for Android is ludicrously large.
Response times for iOS are slow. Windows Phone never materialized.

Should a native application or simply a responsive web app be developed?
Should another version of the solution be made just for mobile devices?
If a native application is created, should it be build on the Microsoft Xamarin platform or on React Nativella?
How should CI and application management be handled along with in-the-cloud versioned APIs?

We have develope mobile applications as parts of large solutions, and have answers to the questions above.